1. Field of the Invention
This invention relates to a process for the production of wheat protein hydrolyzates, in which the multistage hydrolysis is carried out in the presence of selected enzymes, and to the use of the hydrolyzates for the production of light-colored, storage-stable derivatives.
2. Discussion of the Related Art
Degradation products of polypeptides, so-called protein hydrolyzates, have been known for some time. Although they do not have any detergent properties because of the absence of a lipophilic group, they are used in a large number of surface-active formulations by virtue of their dispersing properties and their ability favorably to influence the dermatological compatibility of anionic surfactants by interaction with the protein molecules of the skin. Relevant synoptic articles have been published, for example, by A. Domsch et al. in Arztl. Kosmetol. 13, 524 (1983), by G. Schuster et al. in Cosmet. Toil., 99(12), 63-74 (1984) and by H. Lindner in Parfum. Kosmet., 66, 85 (1985).
Protein hydrolyzates are normally obtained on the basis of animal collagen. In recent years, however, there has been an increasing trend towards vegetable products, for example based on wheat gluten or soya protein.
For example, the hydrolysis of vegetable proteins by special lactic acid bacteria in the presence of hydrocarbons is known from FR-A 25 42 013 (ABC). U.S. Pat. No. 4,757,007 (Nisshin) describes the partial hydrolysis of soya proteins with proteases into fractions differing in their solubility in trichloro-acetic acid, separation of the fractions at a pH value of 7, removal of non-hydrolyzed components and purification of the products by ultrafiltration. European patent application EP-A-0 187 048 (Novo) describes the enzymatic degradation of soya proteins by treatment with special proteases. The production of protein hydrolyzates with an average molecular weight of 500 to 90,000 by step-by-step alkaline, acidic and/or enzymatic degradation of wheat or soya proteins is known from EP-A 0 298 419 (Katayama). Finally, EP-A 0 363 771 (Nestle) reports on a process for the production of protein hydrolyzates in which vegetable proteins are hydrolyzed with hydrochloric acid, non-hydrolyzed components are removed, the hydrolyzates are alkalized to destroy unwanted chlorinated compounds and the resulting products are subsequently acidified.
However, one feature common to all known processes is that, when applied to the vegetable raw material wheat, they give products which, after chemical derivatization, for example after condensation with fatty acid chlorides, discolor and are not sufficiently stable in storage. One particular problem is, for example, that fatty acid condensates of known wheat protein hydrolyzates show an unwanted tendency to cloud in aqueous solution.
Accordingly, the object of the present invention was to provide a solution to the problem of the inadequate stability in storage of derivatives based on wheat protein hydrolyzates.